Fluid catalytic cracking (FCC) is a well-known process for the conversion of relatively high boiling point hydrocarbons to lower boiling point hydrocarbons in the heating oil or gasoline range. Such processes are commonly referred to in the art as “upgrading” processes. To conduct FCC processes, FCC units are generally provided that have one or more reaction zones, with a hydrocarbon stream contacted in the one or more reaction zones with a particulate cracking catalyst. The particulate cracking catalyst is maintained in a fluidized state under conditions that are suitable for the conversion of the relatively high boiling point hydrocarbons to lower boiling point hydrocarbons.
While hydrocarbon streams such as vacuum gas oil, reduced crude, or other petroleum-based sources of hydrocarbons have commonly been upgraded through FCC processes, there is a general desire to upgrade biofuels along with the hydrocarbon streams in the FCC processes. By upgrading biofuel along with the hydrocarbon streams, the resulting upgraded fuel includes a renewable content and enables net petroleum-based hydrocarbon content of the upgraded fuel to be decreased.
Biofuels encompass various types of combustible fuels that are derived from organic biomass, and one particular type of biofuel is pyrolysis oil, which is also commonly referred to as biomass-derived pyrolysis oil. Pyrolysis oil is produced through pyrolysis, including through recently-developed fast pyrolysis processes. Fast pyrolysis is a process during which organic biomass, such as wood waste, agricultural waste, etc., is rapidly heated to about 450° C. to about 600° C. in the absence of air using a pyrolysis unit. Under these conditions, a pyrolysis vapor stream including organic vapors, water vapor, and pyrolysis gases is produced, along with char (which includes ash and combustible hydrocarbon solids). A portion of the pyrolysis vapor stream is condensed in a condensing system to produce a pyrolysis oil stream. Pyrolysis oil is a complex, highly oxygenated organic liquid that typically contains about 20-30% by weight water with high acidity (TAN>150).
Due to the high oxygen content of the pyrolysis oils, pyrolysis oils are generally immiscible with hydrocarbon streams. Prior attempts to co-process pyrolysis oil streams and hydrocarbon streams have involved deoxygenation of the pyrolysis oil followed by combining the deoxygenated pyrolysis oil stream and the hydrocarbon stream prior to FCC processing. Such approaches add unit operations, along with added capital costs, to the upgrading process. Further, clogging of feed lines may still remain a concern even after deoxygenating the pyrolysis oils, and feed lines that facilitate introduction of a pyrolysis oil stream into a reaction zone where FCC processing is conducted are prone to clogging. Additionally, feed lines that contain mixtures of a hydrocarbon stream and a pyrolysis oil stream are also generally prone to clogging due to the presence of the pyrolysis oil stream in the feed lines. Simply separating and introducing the hydrocarbon stream and the pyrolysis oil stream into the reaction zone through separate feed lines is ineffective to avoid clogging.
Accordingly, it is desirable to provide methods and apparatuses that enable a mixture of a pyrolysis oil stream and a hydrocarbon stream to be upgraded through catalytic cracking, such as in fluid catalytic cracking units, while avoiding excessive clogging of feed lines. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.